Core Construction is Vital to Cable Life

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Most construction failures are easy to identify—from the inside. The evidence is in the tear down. We see quite a few catastrophic power cable breakdowns, and unfortunately, symptoms are not usually apparent until after premature failure happens. Our experience has shown construction failures most often occur due to poor conductor bundling, an improperly sized and designed core hose, and insufficient coolant flow.

Frustratingly, the internal wire bundle package just isn’t visible unless the cable is torn down. The best designs are secured wire packages to prevent excessive chaff and friction during electrical cycling. Copper conductors forming the wire package are bundled to create the most efficient geometry for bend radius, and to maximize electrical efficiency, thereby reducing power loss. Signs of poor conductor bundling are usually premature wire breakage and damage to the core hose.

Core hose strength is paramount to maintaining cable integrity. Telltale signs of weak core hose construction is use of soft low-durometer rubber compounds of single or 2-ply construction that often collapse offering little structural support. Additionally, perforations cut or drilled into the core hose to allow coolant further weaken the cable core reducing electrical efficiency and integrity of the wire package. Without proper coolant flow conductors can become embrittled, and in the worst cases can catastrophically melt.

A number of well-designed approaches to good core engineering exist. I2r POWER recommends installing and securing high-temperature engineered plastic wedges at the ends of the core hose to uniformly force coolant around the conductor bundle. Additional considerations for cable repair and maintenance include amount of current, cable length, number of cables per phase, amount of coolant, arrangement of cable installation, number and size of copper conductors, as well as terminal design.

Our advice: When it’s time to schedule power cable maintenance, confirm with your supplier that a proper core design is carefully considered.

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